Definition: 7.18: Square Number
A square number is an equal times an equal, or (a plane number) contained by two equal numbers.
Modern Formulation
A square number (or a square) \(s\) is the product of some integer \(a\) with itself, formally
\[s=a\cdot a=a^2.\]
Notes
 A geometrical definition of a square was given in Def. 1.22.
 The following figure shows a geometrical interpretation of a square number
Mentioned in:
Corollaries: 1
Lemmas: 2 3
Proofs: 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
Propositions: 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59
Sections: 60
Solutions: 61 62 63 64 65 66
Thank you to the contributors under CC BYSA 4.0!
 Github:

 nonGithub:
 @Fitzpatrick
References
Adapted from (subject to copyright, with kind permission)
 Fitzpatrick, Richard: Euclid's "Elements of Geometry"
Adapted from CC BYSA 3.0 Sources:
 Prime.mover and others: "Pr∞fWiki", https://proofwiki.org/wiki/Main_Page, 2016